1. Field of the Invention
The present invention relates to a sheet delivery mechanism for a printer, such as an ink-jet printer.
2. Description of the Related Art
A well-known sheet delivery mechanism incorporated into an ink-jet printer is shown in FIG. 16. The ink-jet printer has a substantially U-shaped sheet passage 103 extending from a sheet feed position 100 via a printing position 101 to a sheet delivery position 102.
An ink-jet print head 2 is disposed at the printing position 101. The ink-jet print head 2 is mounted on a carriage, not shown, and reciprocated in directions perpendicular to a sheet feed direction. The ink-jet print head 2 jets ink particles on a sheet P for printing in synchronism with the reciprocating movement of the ink-jet print head 2 and the advancement of the sheet P.
A feed roller 3 feeds, in cooperation with a leaf plate 4, a sheet P from a sheet feed tray 6 disposed at the sheet feed position 100 or a sheet P inserted by hand into a hand-feed passage 110 toward the ink-jet print head 2. The feed roller 3 rotates in the direction of the arrow (FIG. 16) to feed the sheet pressed thereto by the leaf plate 4 toward the ink-jet print head 2.
A sheet delivery mechanism 10A for delivering a printed sheet P printed by the ink-jet print head 2 comprises a delivery roller 11 for advancing the printed sheet P in a delivering direction indicated by the arrow E, and a pressure roller 12 for pressing the printed sheet P against the delivery roller 11. The delivery roller 11 is disposed behind the ink-jet print head 2 on the sheet passage 103 and supported for rotation in the direction of the arrow (FIG. 16). The pressure roller 12 is biased by a spring or the like toward the delivery roller 11 to press the printed sheet P against the delivery roller 11. The pressure roller 12, in general, comprises spur wheels each having a saw-toothed circumference to avoid the transfer of the ink from the printed sheet P to the pressure roller 12.
The feed roller 3 rotates to pull out a sheet P from the sheet feed tray 6 and to insert the sheet P in the sheet passage 103, and the ink-jet print head 2 prints characters or the like on the sheet P in a portion of the sheet P positioned opposite to the ink-jet print head 2. Then, the printed sheet P is delivered by the cooperative action of the delivery roller 11 and the pressure roller 12 to a delivery tray 15 disposed at the delivery position 102. The printed sheet P is placed in the delivery tray 15 with its printed surface facing up.
In FIG. 16, denoted by 19 is a sheet guide serving also as a platen for supporting the sheet P in a flat state and guiding the same to the delivery roller 11.
Problems in this related art will be described hereinafter. When the printed sheet P is delivered to the delivery tray 15 by the delivery roller 11 of the sheet delivery mechanism of the printer shown in FIG. 16, the printed sheet P slides along the printed surface of the printed sheet P printed in the preceding printing cycle and stored in the delivery tray 15. Accordingly, if the ink printed on the preceding printed sheet P is half dried, the printed surface of the preceding printed sheet P previously stored in the delivery tray 15 and the backside of the succeeding printed sheet P are smeared. Such a problem has become increasingly remarkable in recent years in which printing speed has been progressively increased and a plurality of kinds of ink have become used selectively for versatile printing modes.
To solve such a problem, a printer capable of delivering printed sheet P so that the same will not touch the preceding printed sheet P is proposed in U.S. Pat. No. 4,728,963.
As shown in FIGS. 17 and 18, the sheet delivery mechanism of this previously proposed printer has a platen 19A supported for turning in the direction of the arrow, and a printed sheet storage unit having top rails 9A for temporarily supporting a printed sheet P in a horizontal position. The platen 19a is turned in the direction of the arrow when delivering the printed sheet P to allow the printed sheet P to fall by gravity from the top rails 9A into the stacker, not shown, of the printed sheet storage unit.
The ratio of an area for installing the printed sheet storage unit 9A to an area required for installing the printer is large, the size of the printer is increased inevitably and the printer cannot be miniaturized.